Detection method, detection apparatus, and sample cell and kit for detection

Abstract

A sensor chip including a sensor portion that has at least a metal layer deposited on a surface of a dielectric plate is used. A fluorescent-label binding-substance in an amount corresponding to the amount of a detection target substance in a liquid sample binds onto the sensor-portion. The amount of the detection target substance is detected based on the amount of light generated by excitation of a fluorescent label in the fluorescent-label binding substance. An electrified fluorescent substance containing a plurality of fluorescent dye molecules enclosed by a material that transmits fluorescence output from the plurality of fluorescent dye molecules is used as the fluorescent label. The electrified fluorescent substance is attracted to the sensor portion by applying voltage to the liquid sample in a state in which the fluorescent-label binding substance has bound to the sensor portion. In this state, the amount of the detection target substance is detected.

1 . A detection method comprising the steps of:
 preparing a sensor chip including a sensor portion that has at least a metal layer deposited on a surface of a dielectric plate;   binding a fluorescent-label binding substance in an amount corresponding to the amount of a detection target substance contained in a liquid sample to the sensor portion by contacting the liquid sample with the sensor portion;   irradiating the sensor portion with excitation light to generate an enhanced optical field on the sensor portion; and   detecting the amount of the detection target substance based on the amount of light generated by excitation of a fluorescent label contained in the fluorescent-label binding substance, the fluorescent label being excited in the enhanced optical field, wherein an electrified fluorescent substance containing a plurality of fluorescent dye molecules enclosed by a material that transmits fluorescence output from the plurality of fluorescent dye molecules is used as the fluorescent label, and wherein the electrified fluorescent substance is attracted to the sensor portion by applying voltage to the liquid sample in a state in which the fluorescent-label binding substance has bound to the sensor portion, and wherein the amount of the detection target substance is detected in the state in which the fluorescent substance is attracted to the sensor portion.   
   
   
       2 . A detection method, as defined in  claim 1 , wherein a fluorescent substance the surface of which is modified with a functional group that exhibits a polarity at least in the liquid sample is used as the fluorescent substance in the fluorescent-label binding substance. 
   
   
       3 . A detection method, as defined in  claim 1 , wherein the particle size of the fluorescent substance is greater than or equal to 30 nm. 
   
   
       4 . A detection method, as defined in  claim 1 , wherein a counter-electrode is arranged in contact with the liquid sample, and wherein voltage is applied between the counter-electrode and the metal layer on the dielectric plate to apply the voltage to the liquid sample. 
   
   
       5 . A detection method, as defined in  claim 1 , wherein when the fluorescent-label binding substance binds to the sensor portion, first voltage is applied to the liquid sample to attract the electrified fluorescent substance to the sensor portion, and wherein after at least a part of the fluorescent-label binding substance has bound to the sensor portion, application of the first voltage is stopped and second voltage that generates an electric field opposite to the first voltage is applied to the liquid sample to remove the fluorescent-label binding substance that has not bound to the sensor portion from the liquid sample on the sensor portion, and wherein after the fluorescent-label binding substance that has not bound to the sensor portion is removed, the amount of the detection target substance is detected. 
   
   
       6 . A detection method as defined in  claim 1 , wherein plasmons are excited in the metal layer by irradiation with the excitation light to generate the optical field enhanced by the plasmons, and wherein the amount of the detection target substance is detected by detecting, as the light generated by excitation of the fluorescent label, fluorescence output from the fluorescent label by the excitation of the fluorescent label. 
   
   
       7 . A detection method as defined in  claim 1 , wherein plasmons are excited in the metal layer by irradiation with the excitation light to generate the optical field enhanced by the plasmons, and wherein the amount of the detection target substance is detected by detecting, as the light generated by excitation of the fluorescent label, radiation light that radiates from the other surface of the dielectric plate by newly inducing plasmons in the metal layer by fluorescence output from the fluorescent label by the excitation of the fluorescent label. 
   
   
       8 . A detection method, as defined in  claim 1 , wherein the sensor chip includes an optical waveguide layer deposited on the metal layer, and wherein an optical waveguide mode is excited in the optical waveguide layer by irradiation with the excitation light to generate the optical field enhanced by the optical waveguide mode, and wherein the amount of the detection target substance is detected by detecting, as the light generated by excitation of the fluorescent label, fluorescence output from the fluorescent label by excitation of the fluorescent label. 
   
   
       9 . A detection method, as defined in  claim 1 , wherein the sensor chip includes an optical waveguide layer deposited on the metal layer, and wherein an optical waveguide mode is excited in the optical waveguide layer by irradiation with the excitation light to generate the optical field enhanced by the optical waveguide mode, and wherein the amount of the detection target substance is detected by detecting, as the light generated by excitation of the fluorescent label, radiation light that radiates from the other surface of the dielectric plate, the radiation light radiating by newly inducing plasmons in the metal layer by fluorescence output from the fluorescent label by the excitation of the fluorescent label. 
   
   
       10 . A detection apparatus comprising:
 a housing unit that houses a sensor chip including a sensor portion that has at least a metal layer deposited on a surface of a dielectric plate;   an excitation-light irradiation optical system that irradiates the sensor portion with excitation light;   a light detection means that detects light generated by excitation of the fluorescent label in an enhanced optical field generated on the sensor portion by irradiation with the excitation light; and   a voltage application means that applies voltage to the liquid sample when the sensor chip is housed in the housing unit.   
   
   
       11 . A sample cell for detection comprising:
 a base that has a flow path through which a liquid sample flows down;   an injection opening for injecting the liquid sample into the flow path, the injection opening being provided on the upstream side of the flow path;   an air hole for causing the liquid sample that has been injected from the injection opening to flow toward the downstream side of the flow path, the air hole being provided on the downstream side of the flow path; and   a sensor chip portion provided between the injection opening and the air hole in the flow path, wherein the sensor chip portion includes a sensor portion that has at least a metal layer deposited on a sample-contact surface of a dielectric plate that is provided at least as a part of the inner wall of the flow path.   
   
   
       12 . A sample cell for detection, as defined in  claim 11 , wherein the sensor portion includes an immobilization layer that binds to a fluorescent-label binding substance. 
   
   
       13 . A sample cell for detection, as defined in  claim 12 , wherein the fluorescent-label binding substance includes, as a fluorescent label, an electrified fluorescent substance containing a plurality of fluorescent dye molecules enclosed by a material that transmits fluorescence output from the plurality of fluorescent dye molecules, and wherein the fluorescent-label binding substance is immobilized in the flow path on the upstream side of the sensor portion. 
   
   
       14 . A sample cell for detection, as defined in  claim 11 , wherein an optical waveguide layer is provided on the metal layer in the sensor portion. 
   
   
       15 . A kit for detection comprising:
 a sample cell; and   a solution for labeling,   wherein the sample cell includes:   a base that has a flow path through which a liquid sample flows down;   an injection opening for injecting the liquid sample into the flow path, the injection opening being provided on the upstream side of the flow path;   an air hole for causing the liquid sample that has been injected from the injection opening to flow toward the downstream side of the flow path, the air hole being provided on the downstream side of the flow path;   a sensor chip portion provided between the injection opening and the air hole in the flow path, the sensor chip including at least a metal layer deposited on a sample-contact surface of a dielectric plate that is provided at least as a part of the inner wall of the flow path; and   an immobilization layer that is immobilized on the sensor portion, and that binds to a fluorescent-label binding substance,   and wherein the solution for labeling contains the fluorescent-label binding substance that includes, as a fluorescent label, an electrified fluorescent substance including a plurality of fluorescent dye molecules enclosed by a material that transmits fluorescence output from the plurality of fluorescent dye molecules, and wherein the solution for labeling is injected into the flow path to flow down the flow path together with the liquid sample or after the liquid sample has flowed down the flow path.   
   
   
       16 . A kit for detection, as defined in  claim 15 , wherein an optical waveguide layer is provided on the metal layer in the sensor portion.